During network configuration or other network planning exercises, a neighbor list may be defined that identifies a plurality of cells that may be capable of supporting communications between a user equipment (UE) and the network. A neighbor list may identify cells in various manners including, for example, by scrambling codes associated with the cells such as in a Code Division Multiple Access (CDMA) based network or by information regarding frequency in use by the cells in a Time Division Multiple Access (TDMA) based network. This list may be utilized, for example, to perform handover of a cell to another cell, or perform cell reselection from one serving/camped cell to another serving/camped cell.
As currently defined by 3rd Generation Partnership Project (3GPP), handover and cell reselection procedures are limited to cells in a neighbor list that includes a list of available cells. Public land mobile network (PLMN) selection is performed via the available cells, based on the knowledge of which PLMNs are represented by the available cells and the priority among the available PLMNs. Thus, both cell selection and PLMN selection are typically performed based on radio propagation and subscription related criteria without regard for geographic borders (e.g., a border such as a state, national or international border). While this selection method does consider radio propagation and the preference between available PLMNs, it completely ignores the geographic location of the UE.
During routine call routing, the existence of geographic borders is irrelevant since call routing is based on the location of the destination and not based on the location of the originator. However, for certain situations (such as, for example, emergency calls) the existence of geographic borders may become important. In this regard, many countries have shared emergency call handling between regional Public Safety Answering Points (PSAPs), with each PSAP being responsible for dispatching emergency services in a certain geographic area. Such PSAP organizations are applicable within each country and typically not able to dispatch emergency rescue across the border to neighboring countries.
Near a physical border, a UE user could physically be located in a first country, but could be served by a cell that is located in a second country. If the user has an emergency situation and makes an emergency call for assistance, the caller's location may typically be considered in two steps. First, the call routing may be used to identify the PSAP that corresponds to the cell that is serving the user. Second, the PSAP operator may dispatch emergency response units to the address or location of the user. In a situation where the user is actually in the first country, but is served by a cell in the second country, the serving network will route the call to the responsible PSAP of the second country, which will receive the call. The dispatch of emergency response units may be complicated by the fact that emergency calls cannot typically be routed internationally.